The invention relates to a starter bar for guiding and extracting cast strands of various thicknesses in continuous casting plants with arcuate guiding paths supporting the cast strand at opposite sides thereof. The bar is comprised of pivotally connected link bodies whose thickness corresponds to the smallest or slightest strand thickness of the cast strands.
In continuous casting plants one endeavours to extract cast strands of various thicknesses by using a bendable starter bar which can be used for all thicknesses of cast strands. This starter bar thus must have a thickness that corresponds to the slightest thickness of the strands to be cast. In continuous casting plants with arcuate strand guides there occur intermittent movements at the onset of casting when cast strands are extracted that have a greater thickness than the starter bar. This happens because the starter bar contacts the arc-inner strand guiding path when tensile forces act on it, and the arc-outer strand guiding path when compressive stresses act on it which forces or stresses are, caused by the lowering of the cast strand because of its weight as well as the weight of the starter bar. A continuous extraction is only possible when the frictional forces, which occur during the extraction and which counteract the extraction forces, are bigger than the forces caused by the weight of the cast strand and the starter bar and act in the extraction direction. The intermittent extraction therefore mainly occurs until the initial portion of the cast strand is in the area of the guiding path immediately following the mould.
Various proposals have been made for avoiding intermittent extractions of the initial portion of the cast strand. Thus a starter bar comprising link bodies has been provided with springs which, on the one hand, press sliding plates perpendicularly to the strand guiding path and, on the other hand, press the link bodies to the opposite strand guiding path. Although such a starter bar is guided without play independent of the distance between the opposing strand guiding paths, it is expensive and requires complex maintenance because of its many movable parts. Also, due to the spring forces, the friction present between starter bar and the strand guiding paths is greatly increased.
Furthermore, it is known to press a starter bar consisting of link bodies towards the opposite strand guiding path by individual pressure rollers arranged in one of the strand guiding paths. These pressure rollers are distributed over the longitudinal extension of the arcuate strand guide so that the starter bar is guided without play along one of the strand guiding paths. Making such a strand guiding path provided with pressure rollers is expensive and complex. Care must be taken so that no discontinuities in the strand guiding path occur because of the pressure rollers. For these reasons it is desirable to avoid pressure rollers in the strand guide as far as possible. A further disadvantage consists in that it is hardly possible to equip already existing plants with such pressure rollers.